A method to determine the mass of myocardium undergoing infarction following coronary occlusion relative to the mass of myocardium at risk of infarction has been developed in dogs. An in vitro Evan's blue staining method followed by a triphenyl tetrazolium chloride counter-stain has yielded reproducible myocardial infarct sizes when expressed as % infarct per myocardium at risk. This model appears to be suitable for determination of total mass of myocardium salvaged during acute coronary occlusion following an intervention hypothesized to reduce infarct size.